For a start, judging from the pictures, your saddle is too high.

Your legs are straight at the bottom of the pedal stroke, and your toes are pointing downward.

I'd suggest dropping your saddle height so that when the pedal is at the bottom of the stroke, and your heel is on the pedal, your leg is straight, but you shouldn't be stretching. When your foot is placed on the pedal with the ball over the pedal spindle in the 6 o'clock position, there should be a bend in in your leg (around 120 degrees).

I would suggest that in its current position, your seat is making you rock your hips as you reach for the bottom of the pedal stroke, adding to the wear and tear on your butt.

It needs to be fixed before you do your tour. I know only too well what will happen if you don't fix it, and it was only the wise advice from a bike shop mechanic in the middle of nowhere that solved my very painful butt issues on my first tour around 17 years ago.